kevincolby

Hello. I am new to the forum and have a been following it the last 2 months since i bought my 2006 GX470. I have a few questions about the rear suspension.

When i go over speed bumps, the back of the truck bottoms out, and feels like it shifts sideways as if one side is stiffer. This happens about half the time, the other half is firm and seems normal like the front.

I have taken it to Lexus and they could not figure it out, they said i could have a small leak in one of the bags. I bought a pair of OEM used shocks from a local guy who put a lift on his a year ago. His shocks feel firmer overall, but it still happens. I compressed the shocks before i installed them and they extended by themselves. I have run all the test with techstream and everything clicks and turns on, makes some noises.

Few Questions;
Would a leak in one or both bags cause this? Do the bags only control the height of the back, or does it have a noticeable impact on dampening bumps?(More PSI, higher it goes. Cant be stiffer at current hide height)
If it has something to do with the shock, can i find out with TechStream? Im not sure what I need to look for the program, so i will provide a screen shot.
If its the ride height sensors, I found a way to check them and set them with the voltage output. Would these impact the ride quality, or does it only impact the back height of the truck?
If I check the voltage going to the shocks, would this be the full battery voltage, or does it get stepped down from the ride control switch in the cabin? Is there 4 different Voltage settings to control the soft/stiffness?

The guy I got the shocks from also gave me his air bags. Said everything was working when he took it off for his lift. He was saving them in case he sells it in the near future, but said they are going to waste.
I could test his bags, but dosent seem the next thing to do.
Any Suggestions on the next step to take?

Thanks!






GX470 Suspension Techsteam ScreenShot.

ALAN553

SEARCH posts....13 year old truck...its the air bags....there is a pin hole somewhere

kevincolby

Hi Alan, This post wasnt my first "go to" method. I have SEARCHED alot and several hours over the past 2 months. Most issues are with the ride height. I am not having any problem with my ride height. Some of my questions where to help understand how the system works. Wouldnt a pin hole leak make the rear sag? The compressor would turn on to get the the right height then shot off. The pressure is already in the bags, but still happens. More psi would lift it up more,and also make it stiffer. Leak with lower psi would make it sag, probably bouncy too?

Arailt

Yes, the height adjustment is only on the rear suspension. The comfort/sport shock settings affect all four corners though. In case the tech missed it, check your ride height sensors (they hang down just in front of the air bag shroud and connect the upper control arm to the frame). I had similar symptoms and my passenger side sensor had broken because of rust/age.

FWIW my Lexus tech said they rarely see the air bags fail, even on 15 year old GXs. He said the culprit is almost always the motor failing (which they replace with aftermarket motor because the OE units aren't great), followed by bad sensors.

Hope that helps!

ALAN553

gwebster

2Sheds

Diagnosing the issue can be bit tricky. A leaking air bag (or an air leak anywhere) will have your compressor running more than usual...so listen for that.

I just went through replacing my air bags. I found that even though I obviously had a leak that was causing my issue, the system was still capable of holding a certain amount of pressure (i.e. it never went completely flat...it just wouldn't stay completely full).The truck had been bottoming out constantly - the ride was terrible - and of course the compressor was running quite a bit. I paid about $90 for the pair of bags, and it took me less than 2 hours for the job. The toughest part was getting the air line to release out of the old bags. I used a "T" from a batch of vacuum hose fittings, cut it up a bit with a utility knife, and made a release tool that would do the job.

danmm7

Can you please provide more details (or ideally a picture) of the "tool" that you created for this job? Very interested.

I am planning to soon replace the airbags on my GX470, but i am really unsure about the lines and how to release them without destroying them.
Some people suggested to just pull them while shaking them.... but i don't think this will work.

Thanks!!

2Sheds

There may be a smarter/better way to do this, and no doubt there is a legit tool we can buy for this purpose...but this worked for me. I had this stuff laying around and didn't want to wait for a perfect solution, so use at your own risk...

I made 2 tools for this - the first (on left) was made of "universal" refrigerator water/freezer tubing. It worked fine for the first bag...but not so well for the 2nd. The problem is that the plastic tubing is a little soft, and it gets bent with use...so then I made the 2nd tool out of the vacuum tubing "T"...it's harder plastic.

Anyway...you need a tool that has an inside diameter about the size of the air tubing that goes into the bag...but has an outside diameter small enough to fit into the opening that the tube goes into. You basically wrap this tool around the air line, and push into the opening to release. I beveled the leading edge a bit to get it to slide under the release tab more easily. I just popped these into the there, wiggled them around a bit until they would depress the small tab that retains the tubing. Be prepared for a face full of smelly compressed air when you release the first one.

If I remember right I did it like so:

1. turn off air system, wait a bit for system pressure to ( hopefully) release a little
2. drop and remove spare tire
3. safely elevate the rear end as far as you can so the axle drops fully (you really need to get under there)..my rear tires were just barely off the ground maybe 1/4 inch.
4. use tool to release air line (careful it may be brittle). Get face full of air.
5. use wire coat hanger to remove clip that retains the bag into it's mount
(I released one air line while bag was still mounted, did the other one after I had released it...I guess the order doesn't matter as long as you can reach.
6. put new bag in place and secure clip (a helper may be useful here)
7. replace air line (will secure with a firm "click")
8. once both are done carefully lower truck and ensure bags line up in their proper mounts (a helper is a good idea for this)

Hope this helps....

gwebster

Hi, I recognize the is an old post, but I am trying to find out if anyone who has access to techstream can verify what the correct voltage should be for the +B Power Source under the Air Suspension screen. I recently replaced my alternator and the voltage is showing as 1.8v (see attached pic). Prior to alternator replacement, the reading was approx 13.4v. (similar to the voltage shown in pic by the OP). After replacing the alternator, my vehicle is driving much better and I am trying to determine if it could be related to excess voltage at the +B Power Source. I appreciate if anyone who has access to tech stream could verify their reading. Thanks!

Davenlei

iTrader: (1)

I used this tool from Amazon to remove/install the air lines to the new bags.

tz693

Could the height control fuse be blown?

tz693

Could the height control fuse be blown?

MidniteGX

I wonder what it was?
I have new airbags now for about a year and a half. I put them in myself - pretty easy, even on the driveway. Ride can still be a bit more bumpy than usual.
The compressor still works and the system appears to be airtight. Now, I'm thinking about looking at the ride height sensors since they're probably damaged or just too old and need replacement.
I see aftermarket ones available on RockAuto. Has anyone had any experience using these or recommendations of OE over aftermarket?